The present invention relates to an automatic sound level control system which is used for varying the sound level of audio equipment in accordance with a manually selected level and the ambient noise level.
In the case of an audio system used in a relatively noisy environment, such as a radio receiver or a cassette tape player system provided in a motor vehicle, it is preferable to automatically raise the sound level of the audio system from a level preset by the listener in proportion to the increase in the level of ambient noise such as the noise generated by the engine or suspension of the motor vehicle.